How do I determine the number of electon shells in an atom?

Remember the question on homework page #2: How many electrons are in the first shell: 2, how many electrons are in the 2nd, 3rd, etc... : 8.

Let's look at Copper. A Copper atom has a total of 29 electrons: 2 electrons in the first shell, 8 electrons in the 2nd shell, 8 electrons in the 3rd shell, 8 electrons in the 4th shell, and 3 electrons in the 5th shell. Therefore a Copper atom has a total of 5 electron shells.